As computer technologies have been developed recently, simulation systems and computer-aided engineering (CAE) have been widely used in many fields. For example, in the field of automobile design, the design has been performed based on the simulation using a theoretical formula of the whole automobile, which theoretical formula has been constructed by combining the theoretical formula of each part of the automobile. The theoretical formula is generally expressed by a relational expression between design variables such as the properties of the material, the size and the shape of a structure, and characteristic values such as a ride quality and noises. A desired design variable has been determined by performing the simulation of the characteristic values using the theoretical formula.